自交联型油基钻井液降滤失剂的研制与评价

针对传统油基钻井液降滤失剂耐温性能不足、影响体系流变等问题,基于自交联改性思路,以N-羟甲基丙烯酰胺为功能单体,与丙烯酸丁酯和苯乙烯进行乳液聚合,研制了一种自交联型油基钻井液降滤失剂(BSN)。通过红外光谱仪、激光粒度仪和透射电镜表征了BSN的主要官能团、微观形貌和自交联特征。实验结果表明,BSN含有自交联功能基团羟甲基,平均粒径为247 nm,颗粒间具有明显的交联结构。热重测试结果显示,BSN热稳定性良好,初始分解温度高达355℃,显著高于非自交联型的降滤失剂BS(278℃)。在油基钻井液体系中添加1%的BSN,不仅不影响体系流变参数而且能够提高破乳电压,180℃下的高温高压滤失量仅为4 mL,滤失控制能力明显优于非交联型的降滤失剂BS以及3%的传统油基钻井液降滤失剂有机褐煤和氧化沥青。

Development and Evaluation of a Self-Crosslinking Filter Loss Reducer for Oil Based Drilling Fluids

Conventional filter loss reducers for oil based drilling fluids have deficiencies such as low thermal stability and negative influence on mud rheology. To solve these problems, a new self-crosslinking filter loss reducer, BSN, for oil based drilling fluids was developed through emulsion polymerization with N-methylol acrylamide (a functional monomer), butyl acrylate and styrene. The main functional groups, micromorphology and self-crosslinking characteristics of BSN were characterized by infrared spectroscopy, laser particle size analyzer and transmission electron microscopy. It was found that BSN has self-crosslinking functional group of hydroxymethyl. The average particle size of BSN is 247 nm, and obvious particle-particle crosslinking structure can be seen. Thermalgravimetric test results have shown that BSN has good thermal stability, the initial decomposition temperature of which is 355 ℃, greatly higher than its non-self-crosslinking counterpart BS, which is 278 ℃. Addition of 1% BSN in an oil based drilling fluid not only had little effect on the rheology of the drilling fluid, but also improved the electrical stability of the drilling fluid. This oil based drilling fluid had HTHP filtration rate of only 4 mL, indicating that BSN was superior to BS and 3% other conventional filter loss reducers in controlling the filtration rate of oil based drilling fluids.